1. Field of the Invention
The present invention relates generally to minesweeping, and in particular to minesweeping using a magnetic influence cable that is capable of simulating the magnetic signature of a ship passing through saltwater, therein causing influence mines to detonate when they sense the created magnetic signature. The magnetic influence cable is typically deployed from a tow vehicle in a seawater environment, so it is desirable that the cable have good resistance to corrosion due to air, sun, salt, water, and the presence of an electrical current.
2. Prior Art
There are many types of mines used to damage and destroy marine vessels. Magnetic influence mines detonate on sensing a change in the ambient magnetic field. The proliferation of relatively inexpensive mines makes Mine Countermeasures (MCM) a necessary and expensive challenge to counter the proliferation. Minesweeping has historically been conducted by ships with nonmagnetic bottoms (i.e. wood, fiber-glass). However, even ships with a nonmagnetic bottom have a magnetic signature, and this magnetic signature can be detected by influence mines having a sensor that detects changes in the magnetic environment. More recently, aircraft (helicopters) and remotely controlled unmanned vessels have been employed to conduct minesweeping.
Examples of minesweeping methods include mechanical sweeps, acoustic sweeps, and magnetic sweeps. Mechanical sweeps are designed to sever the cables of moored mines with explosives or abrasives. Acoustic sweeps are typically used to locate the positions of mines, which can then be neutralized, typically by explosives. Magnetic sweeps typically simulate a ship's magnetic signature, thus causing the mine to detonate.
Magnetic influence minesweeper methods generate an electromagnetic current to create a magnetic field that simulates the magnetic signature created by the passage of a ship, thus “tricking” the magnetic influence mine to detonate. A node in the electromagnetic current typically is an electrode connected to a cable that is towed by a vessel or helicopter, usually in saltwater. Saltwater is conductive, and thusly can act as a leg in an electrical circuit when conducting a magnetic sweep. Saltwater is also corrosive, and it is especially corrosive to electrodes, where the electrode is in contact with an electrical current, saltwater, sun, and air. With open loop sweeps, the electrodes are in contact with at least three of these.
The rapid corrosion experienced by these prior art electrodes require frequent replacement of the aft electrode, which requires a connector between the said electrode and the rest of the cable to facilitate the removal and replacement of the electrode. However, the connector itself is subject to frequent failures from fatigue due to the constant movement of the joint in the seawater during towing operations as well as stresses placed on the joint when it is wound around the winch when stowed. Additionally, these connectors are bulky relative to the rest of the cable and can cause snagging and other associated problems when the cable is being wound around the winch during deployment or stowage operations. This is especially problematic when the cable is being deployed from an unmanned minesweeping vessel, where there are no personnel onboard to “unsnagged” or otherwise correct the problem.